The instant invention relates to an optical path folding system and more particularly to such a system utilizing a pair of mirrors forming an acute angle therebetween for compact packaging of scanning devices or line imaging optical systems.
There are many applications in which it is desirable to decrease the length of an optical path, the primary reason being to reduce the space needed for an optical system ensconced in a larger piece of equipment. One example of the need for conserving space is the modern electrophotocopier, in which a complex and bulky optical system is utilized to project an image of an original document onto a photoconductive surface. Photocopiers can be made considerably smaller if their optical systems can be reduced in size. It is similarly desirable to shorten the required separation between a scanning mechanism such as a laser scanner, and a scanned surface, or between a lens and a line image or object.
One device which serves to shorten the required separation between the various elements in an optical system is an optical path folding system including a first mirror and a second mirror opposing the first mirror and forming an acute angle therewith, the mirrors being separated by a predetermined distance, whereby one end of the mirrors is more open than the other end of the mirrors, as described in co-pending patent application Ser. No. 311,696 filed Oct. 15, 1981 and assigned to Pitney Bowes Inc.
When the separation between the mirrors described hereinabove is increased, the optical path length between the two mirrors increases at a faster rate than the separation. If such a pair of mirrors is moved on a traveling carriage so that the distance moved were compensated for by changing the mirror separation, a great distance of carriage travel could be compensated for with a relatively small change in mirror separation.
The instant invention accordingly provides a mechanical means of insuring accurate mirror alignment and separation throughout the carriage travel.